The degree of automation in manufacturing has continuously risen over the years as a result of new developments and improvements in computer technology. The driving force behind automation has been, and continues to be, the desire on the part of manufacturers to reduce labor requirements in a cost-effective manner, and to improve quality. To better realize these goals, most modern-day manufacturing facilities utilize automation to some degree, particularly those which are involved in the mass production of parts.
For example, numerically controlled machines or work stations have been commonplace in many manufacturing facilities for years. A more recent trend in automation is the development of manufacturing "cells" where a cell controller, or central computer, automatically coordinates a network of individually programmable work stations that carry out the various stages and processes required to produce a given part, or a set of related parts.
An automated "cell" generally manufactures parts by following predefined plans that deterministically order how each part should be made, generally as a sequential series of steps that are implemented at individual work stations. In addition to coordinating the work stations, the cell controller continuously verifies the completion of process techniques and steps from one work station to another. This is generally accomplished via a combination of sensor technology and microprocessor-based communications from individual work stations. The cell controller automatically detects an error, or an "exception," in the part's manufacture, and interrupts further operation of any one or more work stations in the cell until the error is corrected.
It is believed that, prior to the development of the present invention, error correction in manufacturing cells (hereinafter referred to as "exception processing") has chiefly been accomplished via manual means. That is to say, although the cell controller may have the capability of identifying the nature of an error, it does not have the capability of informing the human operator as to why or how the error occurred.
By way of illustration, the cell controller may indicate to the operator that a part is not properly positioned at some stage in the cell. However, it does not have the capability of informing the operator as to whether or not the improper position was caused by a materials problem (e.g., the part has an inherent dimensional defect), or an equipment problem involving an electronic or mechanical failure in some portion of a work station. It has always been left to the operator to discern the nature of the problem, and then fix it. In some cases, the operator has the capability to make the fix himself. In other cases, the operator calls in outside maintenance people having expertise beyond the operator's capabilities.
Past experience has shown that when an exception occurs in a manufacturing cell, as much as 80% of the total time required to fix or correct the exception is spent in simply identifying the cause of the exception, or in other words, identifying what is wrong. The remaining 20% is spent in physically implementing corrective action. For this reason, an automated tool having the capability of more efficiently ascertaining the cause of exceptions, and nothing else, would result in significant cost savings to the manufacturer.
As a person skilled in the art would know, automated manufacturing is evolutionary in nature. The degree of automation has progressed to higher and higher levels with new improvements in technology and an ever-expanding knowledge base of learned experience In reality, there are probably no fully automated manufacturing cells in existence today. In other words, virtually all "automated" cells are semi-automatic in the strictest technical sense, because all require, to varying degrees, some form of monitoring or control by human operators. In many cases, this may be no more than a person monitoring a CRT. In certain cases, it may involve a person physically handling materials during some stage of cell operation.
As will become apparent, the invention disclosed here provides yet another evolutionary advance in automated manufacturing cells that has heretofore been unknown in the art. First, it provides a tool that significantly improves the efficiency of both detecting and correcting exceptions in manufacturing cells, and correspondingly reduces the costs associated with past methods of manually correcting exceptions. Second, and just as important, it provides a tool that anticipates exceptions, and maintains better process control over a cell's operation. The end result is that the invention improves the overall quality of the parts produced by the cell.